High School Chemistry  ·  Practice by Skill

Gas Laws Practice Problems

Gas laws describe how the pressure, volume, temperature, and amount of a gas depend on each other. Most problems are about picking the right law and putting temperature in kelvins. Practice below covers pressure units, Boyle's and Charles's laws, the combined gas law, and PV = nRT.

What you’ll practice

  • Pressure and temperature units: convert among atm, torr, and kPa, and always convert to kelvins.
  • Single-variable laws: use Boyle's, Charles's, and Gay-Lussac's laws when one quantity stays constant.
  • Combined gas law: handle problems where pressure, volume, and temperature all change.
  • Ideal gas law: use PV = nRT to connect a gas to moles, including at STP.

Learn the method first →

A quick example: Charles's law

A gas takes up 3.00 L at 300 K. It is heated to 450 K at constant pressure. What is the new volume?

Volume and temperature are directly related, so V2 = V1 × (T2 ÷ T1) = 3.00 L × (450 K ÷ 300 K).

The new volume is 4.50 L.

3 free gas laws problems

Give each one a real try before you open the solution. Your answer is checked as soon as you submit it, and the worked solution shows every step so you can see exactly where a setup went wrong.

#1Pressure Units
Convert 2.50 atm to torr. (1 atm = 760 torr)
#2Boyle's Law
A gas is at 2.00 atm in a 3.00 L container. The volume is doubled at constant temperature. The new pressure is…
#3Combined Gas Law
A gas occupies 2.50 L at 720 torr and 15°C. What volume does it occupy at STP (0°C, 760 torr)? (Convert temperatures to Kelvin: K = °C + 273)

Questions you might have about gas laws

How do I know which gas law to use?
Look at which quantities change and which are held constant. Constant temperature points to Boyle's law, constant pressure to Charles's law, and constant volume to Gay-Lussac's law. If all three change, use the combined gas law.
Why do gas law problems need Kelvin?
The gas laws depend on the true amount of thermal energy, which is zero at 0 K. Celsius has a zero that is arbitrary, so using it gives wrong ratios. Convert with K = °C + 273.
What is the ideal gas law?
PV = nRT links pressure, volume, moles, and temperature for a gas. R is the gas constant, 0.0821 L·atm/(mol·K) when pressure is in atm and volume is in liters.
What is STP?
STP stands for standard temperature and pressure: 0 °C (273 K) and 1 atm (760 torr). At STP, 1 mole of an ideal gas takes up about 22.4 L.
High School Chemistry · Gas Laws Practice Problems